The present invention relates generally to amplitude-modulated lasers. More specifically, but without limitation thereto, the present invention relates to a short cavity amplitude-modulated laser.
Generally, lasers capable of high modulation rates in the gigahertz range are either laser diodes modulated by electrical drive current or solid-state lasers modulated by an external amplitude modulator such as an acousto-optical modulator. Laser diodes are capable of high modulation rates but have poor coherence, generate optical energy at multiple wavelengths, and have limited output power. On the other hand, acousto-optical modulated lasers have a relatively limited bandwidth and poor optical efficiency.
The present invention relates to an amplitude-modulated laser capable of relatively high modulation rates, e.g. up to 15 Ghz. It has applications in high-bandwidth communications systems and other applications that utilize modulated optical energy.
In one aspect of the invention, a short cavity diode-pumped laser generates optical energy that may be modulated over a wide range of frequencies. In one embodiment, the short cavity diode-pumped laser may be modulated at rates up to 15 GHz. The short cavity diode-pumped laser may include a laser diode modulator and a laser coupled to the laser diode modulator having a cavity lifetime of less than about 100 picoseconds.
In another aspect of the invention, the short cavity diode-pumped laser is pumped by the laser diode modulator in response to an electrical current or voltage. The laser diode modulator may include a laser diode, a DC bias source coupled to the laser diode, and an electrical modulation source coupled to the DC bias source. The electrical modulation source may be, for example, a signal generator. The laser diode modulator may generate pump energy having a pump wavelength in the range from about 610 nm to about 1000 nm.
In another aspect of the invention, the short cavity diode-pumped laser generates a laser output from a variety of laser gain elements suitable for short cavity laser configurations. In one embodiment, the laser includes a laser gain element of crystalline Nd:YAG or Cr:LiSAF. In another embodiment, the laser gain element contains a laser dye. The laser dye may be contained in a liquid, a gas, a solid, or a gel, and may include rhodamine 700 dye. The laser dye may be contained in a polymethylmethacrylate host having a thickness of about 100 microns.
In a further aspect of the invention, pump energy is focused onto the laser gain element. In one embodiment, the laser includes a focusing lens for focusing pump energy from the laser diode modulator onto the laser gain element.